The present invention relates to heat exchangers and more particularly to heat exchangers used as coolers, for example as cooling radiators of a heat engine.
Although not exclusively, the invention relates more particularly to heat exchangers used on heavy-truck vehicles the end tubes of which are often submitted to important stresses, both thermal and mechanical stresses, which makes it necessary to reinforce the connection between the tubes and the tube end plates.
The hereinabove mentioned problem is well-known of the man skilled in the art, and it has already been proposed to reinforce the tube end plates near the end rows of tubes. For doing so, it has been proposed to place reinforcing plates engaged on the ends of the tubes either above or beneath the tube end plates.
Applicant has already proposed in French Pat. No. 73 39956 (published under N.degree. 2,250,973) to make reinforcing plates forming successive corrugations in the top of which are made apertures for passing the tubes, these corrugations being used for holding the brazing alloy between them and the top of a tube end plate. It results therefrom that the connection between the tubes and the tube end plates is considerably reinforced.
It has been shown in use that the solutions as proposed were satisfactory by permitting the heat exchangers to resist both mechanical and thermal stresses. However, it has appeared that the improvement which has been brought, although satisfactory for the present obligations of use, did not reach the degree which could be expected.
Another solution had also been proposed in British Pat. No. 622,421 in which two tube end plates form opposite collars.
The state of the art concerning connection between a tube end plate and tubes is also shown by German Pat. No. 703,758; British Pat. Nos. 1,288,561 and 731,431; French Pat. No. 73-27198 (published under No. 2,238,545); and U.S. Pat. Nos. 2,488,627; 2,229,207; and 4,272,006.
It has then been found that the connections through brazing between the reinforcing plates, on the one hand, and the tube end plate and tube, on the other hand, were not perfect because of defects in the brazing alloy which were due to a presence of bubbles following boiling of the flux solvent.
According to the invention, it has consequently been found that it was necessary to reduce as far as possible the defects of the brazing alloy and be sure that a flow of brazing alloy is suitably made upon the connecting step i.e. without the presence of the above-mentioned bubbles.